The invention relates to methods and apparatus for controlling the flow of air in a combine, especially a combine with a self-leveling shoe assembly.
A significant advance in the field of harvesting farm products is the addition of a reciprocating shoe assembly to a combine. A quantity of air is blown over a pair of reciprocating sieves. The combination of reciprocating motion and airflow separates the harvested product from unwanted chaff. By careful control of the flow of air, the oscillating motion of the sieves, and the location of the shoes, the separated product is fed into one auger, and the unwanted chaff is discharged.
However, as the combine traverses along the side of a hill, the efficiency of separation by the shoes is affected by the inclination of the combine. With the advent of the self-leveling shoe assembly (such as that described in U.S. Pat. No. 4,344,443 incorporated herein by reference), the efficiency of separation is somewhat restored. The self-leveling feature permits the pair of reciprocating sieves to stay in a more constant orientation relative to gravity, and the harvested product is more consistently separated.
However, one problem with some self-leveling shoe assemblies is inadequate control of air flowing within the combine. In some applications, the lower seal between the bottom of the shoe assembly and the static floor of the combine is fixed such that underside gaps are created when the shoe assembly pivots to maintain level operation. Air is permitted to flow through this unwanted gap, which affects the pattern of air flowing over the sieves for separation of the product. Separation is thus made less efficient. Further, in some self-leveling shoes there are largely unsealed gaps on the lateral sides of the shoe assembly (gaps between the lateral sides of the pivoting structure and the non-pivoting, static structure that faces the pivoting structure). In these applications, air can flow unimpeded around the sides of the self-leveling shoe, even when the combine is level and the shoe is not pivoted.
What is needed are apparatus and methods for improved airflow control of self-leveling shoes. The present invention does this in novel and unobvious ways.